1. Field of the Invention
The present invention generally relates to a projector. More specifically, the present invention relates to a projector having a cooling arrangement to cool an optical arrangement.
2. Background Information
DLP (Digital Light Processing®) projector is a reflecting type of display device. In the DLP projector, light from a light source is filtered, and the light is reflected on a DMD (Digital Micromirror Device). The DMD is a semiconductor element. The light reflected on the DMD is expanded and projected by a lens. Then, image colorization is performed.
The DLP projector includes a light source, an optical engine system and an external housing. The optical engine system includes a color wheel, a light tunnel, a DMD and a housing that houses the color wheel, the light tunnel and the DMD. The external housing houses the light source and the housing. When the light source generates heat up to a high temperature, the color wheel, the light tunnel, and the DMD located on a light path of the light emitted from the light source are heated up, too. The elevation in temperature cause operating performance and durability of the color wheel, the light tunnel and the DMD to be diminished.
In view of this, a heat sink is attached to the DMD and a fan is provided to the external housing. The heat sink is exposed to an outside of the housing. The fan blows cooling air through an inside of the external housing to promoted heat dispersal by the heat sink, to suppress temperature elevation of the DMD, and to suppress temperature elevation of the light tunnel and the color wheel.
With conventional projectors, cooling is performed by blowing air against optical elements used in the projectors.
For example, a fan is used for sending cooling air through an interior of an external housing (see Japanese Patent Utility Model Registration 3,108,585, for example).
With a conventional projector, a duct is used to blow cooling air along a fixed path. Specifically, the cooling air is circulated in the duct with a fan (see Japanese Laid-Open Patent Application Publication No. 2003-337380, for example). Then, heat exchange is performed by blowing the cooling air, which has cooled along a circulation path, against hot optical elements (such as the light tunnel). Furthermore, the cooling air that has been heated through the heat exchange is cooled again. With another conventional projector, cooling air is drawn in by a sirocco fan. The cooling air is passed through a duct and guided to a light source unit (see Japanese Laid-Open Patent Application Publication No. 2006-293117, for example). With another conventional projector, cooling air discharged from a cooling fan blows at the DMD (see Japanese Laid-Open Patent Application Publication No. 2006-259282, for example).
Furthermore, with conventional projectors, cooling methods involves liquid cooling (see Japanese Laid-Open Patent Application Publication No. 2006-259282 and Japanese Laid-Open Patent Application Publication No. 2007-127856, for example).
However, with the conventional projector, the cooling air from the fan is diffused in the interior of the housing. Thus, it is difficult to raise the efficiency of cooling the DMD. The same can be said about the efficiency of cooling the light tunnel or the color wheel.
In contrast, Japanese Laid-Open Patent Application Publication No. 2003-337380 involves cooling the light tunnel by utilizing a heat exchange cycle of air circulating through the duct. Thus, extra space in which to install a ring-shaped duct is required. Furthermore, an extra air drying agent is also required. Thus, the temperature of the circulating air rises gradually, which worsens cooling efficiency.
Furthermore, with Japanese Laid-Open Patent Application Publication No. 2006-293117, the cooling air discharged through the duct into the interior of the light source unit flows through the interior of the housing. Thus, the cooling air flowing through the interior of the housing becomes hot. Then, it is difficult to obtain low-temperature cooling air for efficiently cooling the light tunnel and the DMD.
Furthermore, with Japanese Laid-Open Patent Application Publication No. 2006-259282, the cooling air discharged from a cooling fan is blown towards the DMD from the duct. The cooling air blown out of the duct contacts with the DMD, which improves the DMD cooling effect to a certain extent. However, when the cooling air blown from the duct contacts with the DMD, it is diffused, which means that the DMD cooling efficiency cannot be increased markedly.
In addition, employing a liquid cooling type of cooling method as indicated in Japanese Laid-Open Patent Application Publication No. 2006-259282 and Japanese Laid-Open Patent Application Publication No. 2007-127856 is impractical in terms of providing a projector that is simple and easy to handle because it requires a relatively large mechanism such as a radiator, a duct, a water pump, or the like.